I have a customer that has a fairly large lylac that they want to scale back about half way. I have never pruned one this drasticly, is there anything i should know about them before i start. Im thinking i should wait until winter before i do anything so that the sap is down. Is this right?
Renovation in the winter is best, but be sure the customer knows that they flower on the previous year's wood; you are removing that wood, so the Lilacs won't flower next year, and may even be mad enough at you that they won't flower for longer than that. If you're just pruning to shape, do it in the summer after flowering.
Don't prune the tips off, take out the bigger older trunks down to the ground and leave the smaller ones to take thier place. there should be plenty of suckers coming up between the large ones. As you take the big ones out you will start to see how much smaller it's going to be.
I agree with Todd. Removing the oldest wood will give a better result and will help keep the lilac vigorous and naturally shaped.
Every thing above is true. Make sure to convince them to wait until after flowering to prune. Its only a few more months away. It'll pay off for them in the end. Prune shortly after flowing and never take more than 20% if you can. Don't worry, if necessary you can take 50% but it isn't the best case scenario.
